Did anyone suggest fslint?  Apart from finding unnecessary files, duplicates
and broken links, there's an education to be had in clever scripting behind it all:
*********************************************************************************************************
#!/bin/bash

# findup - find duplicate files
# Copyright © 2000-2006 by Pádraig Brady <P@draigBrady.com>.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
# See the GNU General Public License for more details,
# which is available at www.gnu.org


# Description
#
#    will show duplicate files in the specified directories
#    (and their subdirectories), in the format:
#
#    2 * 2048    file1 file2
#    3 * 1024    file3 file4 file5
#    2 * 1024    file6 file7
#
#    Where the number is the disk usage in bytes of each of the
#    duplicate files on that line, and all duplicate files are
#    shown on the same line.
#        Output it ordered by largest disk usage first and
#    then by the number of duplicate files.
#
# Caveats/Notes:
#    I compared this to any equivalent utils I could find (as of Nov 2000)
#    and it's (by far) the fastest, has the most functionality (thanks to
#    find) and has no (known) bugs. In my opinion fdupes is the next best but
#    is slower (even though written in C), and has a bug where hard links
#    in different directories are reported as duplicates sometimes.
#
#    This script requires uniq > V2.0.21 (part of GNU textutils|coreutils)
#    undefined operation if any dir/file names contain \n or \\
#    sparse files are not treated differently.
#    Don't specify params to find that affect output etc. (e.g -printf etc.)
#    zero length files are ignored.
#    symbolic links are ignored.
#    path1 & path2 can be files &/or directories

script_dir=`dirname $0`                #directory of this script
script_dir=`readlink -f "$script_dir"` #Make sure absolute path

. $script_dir/supprt/fslver

Usage() {
    ProgName=`basename "$0"`
    echo "find dUPlicate files.
Usage: $ProgName [[-t [-m|-d]] [-r] [-f] paths(s) ...]

If no path(s) specified then the currrent directory is assumed.

When -m is specified any found duplicates will be merged (using hardlinks).
When -d is specified any found duplicates will be deleted (only 1 left).
When -t is specfied, only report what -m or -d would do.

You can also pipe output to $script_dir/fstool/dupwaste to
get a total of the wastage due to duplicates.

Examples:

search for duplicates in current directory and below
    findup or findup .
search for duplicates in all linux source directories and merge using hardlinks
    findup -m /usr/src/linux*
same as above but don't look in subdirectories
    findup -r .
search for duplicates in /usr/bin
    findup /usr/bin
search in multiple directories but not their subdirectories
    findup -r /usr/bin /bin /usr/sbin /sbin
search for duplicates in \$PATH
    findup \`$script_dir/supprt/getffp\`
search system for duplicate files over 100K in size
    findup / -size +100k
search only my files (that I own and are in my home dir)
    findup ~ -user \`id -u\`
search system for duplicate files belonging to roger
    findup / -user \`id -u roger\`"
    exit
}

for arg
do
    case "$arg" in
    -h|--help|-help)
        Usage ;;
    -v|--version)
        Version ;;
    --gui)
        mode="gui" ;;
    -m)
        mode="merge" ;;
    -d)
        mode="del" ;;
    -t)
        t="t" ;;
    *)
                argsToPassOn="$argsToPassOn '$arg'"
    esac
done
[ "$mode" = "merge" ] && argsToPassOn="$argsToPassOn -xdev"

if [ ! -z "$mode" ]; then
    forceFullPath="-f"
    sep_mode="prepend"
else
    sep_mode="none"
fi

if [ "$mode" = "gui" ] || [ "$mode" = "merge" ] || [ "$mode" = "del" ]; then
    merge_early=""    #process hardlinks
else
    merge_early="-u"  #ignore hardlinks
fi

. $script_dir/supprt/getfpf $forceFullPath "$argsToPassOn"

check_uniq

if [ `find . -maxdepth 0 -printf "%D" 2> /dev/null` = "D" ]
then
    devFmt="\060" #0
else
    devFmt=%D #This is new and will help find more duplicate files
fi
                     #print name, inode & size.
find "$@" -size +0c -type f -printf "$FPF\0$devFmt\0%i\0%s\n" |
tr ' \t\0' '\0\1 ' | #remove spaces, tabs in file names
sort -k2,2n -k4,4nr -k3,3 $merge_early |#group [and merge] dev,size & inodes
if [ -z "$merge_early" ]; then
    $script_dir/supprt/rmlint/merge_hardlinks
else
    uniq -3 -D       #pick just duplicate filesizes
fi |
sort -k3,3n |        #NB sort inodes so md5sum does less seeking all over disk
cut -f1 -d' ' -s |   #get filenames to work on
tr '\0\1\n' ' \t\0' |#reset any space & tabs etc and delimit names with \0
xargs -r0 md5sum -- |#calculate md5sums for possible duplicates
sort |               #group duplicate files together
tr ' \t' '\1\2' |    #remove spaces & tabs again (sed can't match \0)
sed -e 's/\(^.\{32\}\)..\(.*\)/\2 \1/' | #switch sums and filenames

# The following optional block, checks duplicates again using sha1
# Note for data sets that don't totally fit in cache this will
# probably read duplicate files off the disk again.
uniq --all-repeated -1 | #pick just duplicates
cut -d' ' -f1 |          #get filenames
sort |                   #sort by paths to try to minimise disk seeks
tr '\1\2\n' ' \t\0' |    #reset any space & tabs etc and delimit names with \0
xargs -r0 sha1sum -- |   #to be sure to be sure
sort |                   #group duplicate files together
tr ' \t' '\1\2' |        #remove spaces & tabs again (sed can't match \0)
sed -e 's/\(^.\{40\}\)..\(.*\)/\2 \1/' | #switch sums and filenames

uniq --all-repeated=$sep_mode -1 | #pick just duplicates
sed -e 's/\(^.*\) \(.*\)/\2 \1/' | #switch sums and filenames back
tr '\1\2' ' \t' |    #put spaces & tabs back

if [ ! -z "$mode" ]; then
  cut -d' ' -f2- |
  if [ ! $mode = "gui" ]; then # external call to python as this is faster
    if [ -f $script_dir/supprt/rmlint/fixdup.py ]; then
        $script_dir/supprt/rmlint/fixdup.py $t$mode
    elif [ -f $script_dir/supprt/rmlint/fixdup.sh ]; then
        $script_dir/supprt/rmlint/fixdup.sh $t$mode
    else
        echo "Error, couldn't find merge util" >&2
        exit 1
    fi
  else
    cat
  fi
else
(
psum='no match'
line=''
declare -i counter
while read sum file; do           #sum is delimited by first space
  if [ "$sum" != "$psum" ]; then
    if [ ! -z "$line" ]; then
       echo "$counter * $line"
    fi
    counter=1
    line="`du -b "$file"`"
    psum="$sum"
  else
    counter=counter+1             #Use bash arithmetic, not expr (for speed)
    line="$line $file"
  fi
done

if [ ! -z "$line" ]; then
  echo "$counter * $line"
fi
) |
sort -k3,3 -k1,1 -brn
fi
*************************************************************************************************************